Idarubicin-labeled electrochemical biosensor for detection of circulating tumor cells in colon cancer patients.

A disposable electrochemical biosensor was developed for the early diagnosis of metastatic colon cancer through the detection of circulating tumor cells (CTCs), labeling with the electroactive anticancer drug, idarubicin (IDA) as a redox indicator. The sensing platform was constructed by modifying screen-printed carbon electrodes (SPCEs) layer-by-layer with multi-walled carbon nanotubes and poly-terthiophene benzoate, followed by the covalent immobilization of a colon cancer-specific aptamer (W3). Sequential modification of each sensing layer was confirmed via surface and electrochemical characterization experiments. Biocompatibility of the sensing components was initially validated through cytotoxicity assays, demonstrating high cell viability (92.8 %). Under optimized conditions, the biosensor achieved an excellent detection sensitivity, capable of identifying as few as three CTCs spiked in 1.0 mL whole blood using square-wave voltammetry. The sensor exhibited excellent analytical performance, with high accuracy (≥89.6 %), precision (coefficient of variation ≤5.1 %), anti-interference capability (relative interference effect ≤5 %), reproducibility (relative standard deviation ≤ 3 %), and operational stability for up to 36 days under laboratory-controlled conditions. The feasibility of the proposed sensor for practical application was validated through a preliminary clinical study involving five healthy volunteers and five colon cancer patients. Among them, one patient was identified as being at high risk for metastasis, presenting with 24 CTCs/mL, while the remaining four were classified as moderate-risk cases, with CTC levels ranging from 4 to 9 cells/mL.